A conventional stem-type semiconductor laser to be used in a CD-use pickup and the like, which has been disclosed by, for example, Japanese Patent Application Laid-Open No. 2001-111152, has a structure as shown in FIG. 5. In other words, a metal material such as iron is formed through a cold forging method, and one portion of the center of a base 61 is raised to form a heat sink portion 62 to which leads 63 and 65 are secured through glass 66 or the like to form a stem 60, and a laser chip 71 is mounted on this heat sink portion 62 through a sub-mount 74 made of a silicon substrate and the like, with one of electrodes (on the rear side of the chip 71) being electrically connected to the lead 63 by a wire 73 through a relay portion 78 of the sub-mount 74, while the other electrode is connected to the sub-mount 74 through the wire 73, so that it is electrically connected to a common lead 64 via the heat sink portion 62 and the base 61 through the rear surface.
Here, reference numeral 72 represents a monitor-use light-receiving element one of electrodes of which is connected to the lead 65 through the wire 73, while the other electrode is electrically connected to the common lead 64 through the sub-mount 74, the heat sink portion 62 and the base 61. Further, a cap 75 is put on the periphery thereof; thus, the semiconductor laser is formed. A through hole 75a is formed in the center of the top portion of the cap 75 so that light, emitted by the laser chip 71, is transmitted through it, and a glass plate 76 is attached thereto by using an adhesive 77 so as to seal the through hole.
As described above, with respect to the conventional semiconductor laser to be used in a pickup for a CD, a DVD and the like, a package having a can-type structure in which the leads 63, 64 and 65 are secured to the metal base 61 so that the laser chip 71 is secured to the heat sink 62 connected to the base 61 has been mainly used. For this reason, this structure has good heat conduction, and also has a high airtight property with superior reliability since it is covered with the metal cap 75 on the periphery thereof; however, in this structure, since the leads 63 and 65 need to be sealingly bonded by using glass 66 or the like, the resulting problems are that it is not possible to shorten the diameter of the stem 60, that a number of parts are required and that complex manufacturing processes are required to cause high costs.
In recent years, along with the current cost reductions in electronic apparatuses including, in particular, personal computers, there have been strong demands for cost reduction also in semiconductor lasers to be used for pickups and the like. For this reason, there have been demands for improvements on the laser chip side in an attempt to improve resistance of the laser chip against external air, by using an inexpensive mold-type structure using a lead frame and a resin mold, which is completely the same structure as the conventional can-type structure.